The present invention relates to a plasma processing apparatus and a plasma processing method in which a substrate-like sample such as a semiconductor wafer is processed and, more particularly, to a plasma processing apparatus and a plasma processing method in which etching processing is processed on a sample using plasma generated in a processing chamber disposed in a vacuum vessel by supplying process gases into the processing chamber through gas piping.
In fabrication of semiconductor devices, a plasma processing apparatus using plasma is widely used. In an etching processing apparatus, in particular, a semiconductor wafer is held on a stage within a processing chamber disposed in a vacuum vessel, an electric or magnetic field is supplied into the processing chamber while process gases suitable for processing of materials of a structure of a thin film for configuring semiconductor circuits which is formed in advance on a top surface of the semiconductor wafer are supplied into the processing chamber so that particles of the process gases are excited to generate plasma, and the film structure is processed along a mask arranged thereon.
In such a step of performing processing of a film structure on a semiconductor wafer, a gas containing a substance highly reactive with silicon (which is denoted merely by Si, hereinafter) compound which forms a semiconductor circuit structure, aluminum (which may be denoted merely by Al, hereinafter) alloy, or the like or, for example, a halogen-based element is generally used. As for gas supply lines for supplying such a gas into a processing chamber within a vacuum vessel, materials of excellent corrosion resistance are used in general for a member in contact with the gas or, in particular, gas supply piping which is a member used in gas introduction lines; for example, a stainless steel (SUS316L in Japan Industrial Standard designation) is used for an inner wall of a pipe for supplying a gas containing chlorine or a compound thereof as an element of a composition.
Nevertheless, an etching apparatus of a prior art has a problem that elements of iron (Fe), chromium (Cr), and nickel (Ni) which composes the stainless steel used for the supply piping reacts mutually with the process gases to form substances which flow along the gas flow into the processing chamber so that surfaces of a sample, the members disposed on the route of sample transfer, or a transfer robot are contaminated as the substances depositing on the top surface of the sample or remaining around its top surface as a gas.
To solve such a problem, in a plasma processing apparatus of a prior art, those with chromium passivity coating formed on the surface are used as members in contact with highly reactive process gases. As such a prior art technique, it is known to form a hard film made of fine particles of chromium (III) oxide (Cr2O3) on the surface of a stainless-steel base material by chemically changing chromium (VI) oxide (CrO3) and as examples of such techniques, those in JP-A-59-009171, JP-A-61-052374, JP-A-63-126682, and JP-A-63-317680 are known.